This invention relates to accurately shaped artificial, all ceramic onlay tooth crowns and inlays as replacement for lost tooth structure. By starting from a negative reproduction of the prepared tooth and then copy milling a surface which will fit into the prepared cavity, a tooth crown or an inlay is obtained which is easier to produce and of lower cost. In addition, the onlay crown or inlay has higher strength and a more accurate shape. Preferably the coping is manufactured from a biocompatible, high strength ceramic material, which is sintered to high density.
Artificial tooth crowns and inlays made from a metal are today manufactured mainly in the following way: A dentist makes a preparation on a tooth, on which a dental construction is to be fixed in the mouth of a patient, an impression is made and with this impression a copy of the preparation is made in gypsum. On this model, a dental technician prepares a crown in wax. The adjacent teeth must be considered, and the dental technician must have models from the two jaws. A sprue former of wax is fixed on one of the cusps of the wax crown. The wax crown is loosened from the gypsum model. The wax crown with the sprue former are invested in a metal ring with investment. The wax is burnt out and a crown can be cast in a precious or non-precious metal. The cast crown can, in certain cases, be covered by a veneer made of porcelain in order to obtain a color of the tooth crown similar to the color of natural teeth. Instead of porcelain, plastic material can be used.
The fabrication of tooth crowns in glass is very close to the technique described above with the difference that after the casting, a thin layer of porcelain is painted on the surface and fired in order to give the tooth crown individual tooth colors.
Tooth crowns fabricated mainly of porcelain can be made with conventional dental porcelain technique from a sheet made of a precious alloy. Porcelain crowns and inlays can also be made with conventional dental porcelain technique on a model of the abutment. The material of this model does not change dimensions on heating up to 1200.degree. C. When the tooth crown or the inlay is ready, the model of the abutment is removed by sand blasting.
The above described complicated and time consuming methods are used to manufacture crowns and inlays, which will fit in individually prepared cavities in natural teeth.
The problem with the material now used (porcelain, glass, etc.) in artificial tooth crowns is their brittleness, which often gives early fracture, and these artificial crowns and inlays must be replaced more or less regularly.